Developing high-performance carbon fiber-reinforced polymer (CFRP) composites that are simultaneously recyclable and flame retardant and have the prepregs long shelf life is a significant challenge in sustainable composites manufacturing. To address this, we synthesized a multifunctional secondary amine curing agent, called T1PI, derived from vanillin. T1PI was synthesized via a Schiff base reaction involving the six-vanillin functionalized cyclophosphazene and 2-(piperazin-1-yl) ethanamine. By utilizing T1PI to cure bisphenol A diglycidyl ether (DGEBA), we fabricated a carbon fiber-reinforced epoxy vitrimer composite (T1PI/DGEBA) with a tensile strength of 490 MPa and a moderate glass transition temperature (T_g) of 139 °C, which are beyond the composite performance requirements for a wide range of applications such as automotive and sports goods. While the curing process of T1PI/DGEBA starts at lower temperatures compared to a commercial amine–epoxy resin system, its curing rate constant at ambient temperature is 11 times lower. This slower curing rate results in a longer shelf life for prepregs made of T1PI/DGEBA compared to a commercial epoxy-diamine system. Uniform incorporation of dynamic Schiff base bonds enabled the epoxy vitrimer to be both thermoformable and chemically recyclable. The use of nondestructive techniques allowed for the recovery of carbon fibers from the CFRP under mild chemical conditions. The T1P/DGEBA CFRP also showed exceptional flame retardancy, attributed to its high N/P content within the network structure. Overall, T1PI exhibits simple production, low curing temperature, and a long shelf life, making it a promising candidate for an efficient curing agent for the fabrication of sustainable CFRP composites.

中文翻译：

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追求可持续复合材料：开发高性能、阻燃且可回收的碳纤维增强环氧 Vitrimer 复合材料

开发同时可回收、阻燃且预浸料具有较长保质期的高性能碳纤维增强聚合物 (CFRP) 复合材料是可持续复合材料制造中的一项重大挑战。为了解决这个问题，我们合成了一种源自香草醛的多功能仲胺固化剂，称为 T1PI。 T1PI 通过涉及六香草醛官能化环磷腈和 2-(哌嗪-1-基)乙胺的席夫碱反应合成。通过利用T1PI固化双酚A二缩水甘油醚（DGEBA），我们制备了碳纤维增强环氧玻璃体复合材料（T1PI/DGEBA），其拉伸强度为490 MPa，玻璃化转变温度（T _g）为139 °C，这超出了汽车和体育用品等广泛应用的复合材料性能要求。与商用胺-环氧树脂体系相比，虽然 T1PI/DGEBA 的固化过程在较低温度下开始，但其在环境温度下的固化速率常数要低 11 倍。与商业环氧二胺系统相比，这种较慢的固化速率导致由 T1PI/DGEBA 制成的预浸料的保质期更长。动态席夫碱键的均匀结合使环氧玻璃体既可热成型又可化学回收。使用无损技术可以在温和的化学条件下从 CFRP 中回收碳纤维。 T1P/DGEBA CFRP 还表现出卓越的阻燃性，这归因于其网络结构中的高 N/P 含量。总体而言，T1PI 具有生产简单、固化温度低和保质期长的特点，使其成为用于制造可持续 CFRP 复合材料的高效固化剂的有前途的候选者。